While Clark (2008) uses the Malthusian model to explain the logic of the preindustrial economy, O'Rourke and Williamson (1999) utilize concepts and terminology taken from the Ricardian model to gain insight into the First Globalization. Why not using the Ricardian model to understand the preindustrial economy and the Malthusian Model for the First Globalization? What makes each model useful for understanding its respective epoch?